Hey! Check out this page I published using Google Page Creator. It include a basic design for a Castor wheel used with the nxt. The main reason for making it was to test out Lego's new LEGO Digital Designer software which makes building instruction out of 3D Lego models you build. Before now it would have taken hours to make this little model, but with LEGO Digital Designer I made this web page and model in under an hour and now I can make them faster because I have figured it out.